Reciprocal changes in feeding behavior produced by intrahypothalamic chemical injections

Abstract

Feeding behavior was studied in rats bearing chronic intrahypothalamic cannulas through which small quantities of chemical substances could be injected from remote microsyringes. Procaine-HCl injected bilaterally into the ventromedial hypothalamic regions in a dose range of 0.5–6.0 µl elicited normal feeding behavior repeatedly in satiated animals. Hypertonic saline injections into the medial hypothalamus suppressed spontaneous eating in hungry animals. Conversely, injections of hypertonic saline into the lateral hypothalamus elicited eating, and eating was suppressed by procaine injections into this same area. Drinking was elicited in a single animal bearing bilateral lateral cannulas. Control injections of isotonic saline did not regularly produce any of these effects. Dextrose injected bilaterally into the ventromedial hypothalamus did not suppress spontaneous eating in food-deprived rats. These results offer additional evidence for the concept that there exists in the hypothalamus a dual mechanism involving a medial inhibitory system of neurons and a lateral excitatory system of neurons functioning reciprocally in the control of food intake.